Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $62.48   4.124%   $65.0567   $65.06   $65.05   $65.10  
  Purchase #2 $165.38   5.397%   $174.3056   $174.31   $174.30   $174.30  
  Purchase #3 $93.66   4.758%   $98.1163   $98.12   $98.10   $98.10  
  Purchase #4 $155.60   4.559%   $162.6938   $162.69   $162.70   $162.70  
  Purchase #5 $172.71   5.741%   $182.6253   $182.63   $182.65   $182.60  
  Purchase #6 $232.99   5.529%   $245.872   $245.87   $245.85   $245.90  
  Purchase #7 $25.81   8.520%   $28.009   $28.01   $28.00   $28.00  
  7 purchase totals = $908.63       $956.6787   $956.69   $956.65   $956.70